...even empty ones.
For packages in `home.packages` with no Fish completions, we build an
empty directory that is not included in our runtime closure (because we
build a collection of symlinks to their contents: if there are no
contents, there is nothing to symlink). This means these empty
completion packages get garbage-collected by Nix. They are not that
expensive to rebuild but there can be enough of them it adds up, and any
change to any package in `home.packages` is enough to trigger a rebuild.
Fix this by forcing a dependency on all of them. Since we already
depended on them anyway if they were non-empty, this only adds
dependencies on empty directories (so should not significantly affect
storage space).
Fixes#6157.
f045bd46b7